The present invention relates to a deployment system for deploying an self expandable cardiac valve prosthesis, the deployment system comprising a first tube and being designed to carry an expandable cardiac valve prosthesis to be disposed over a distal portion of the first tube. The deployment system also comprises a tip, being fixedly connected to the first tube at a distal end of the first tube, wherein the tip is designed, such that it removably accommodates and holds a proximal end of a cardiac valve prosthesis, wherein the tip is slidable distally relative to the prosthesis to release the proximal end of the prosthesis. Furthermore, the deployment system comprises a sheath designed to be disposed over and holding the prosthesis in a compressed state, wherein the sheath is slidable proximally relative to the prosthesis to stepwise release and expand the prosthesis, and a first actuating mechanism being slidable in a proximal direction and being linked to the sheath for stepwise retracting the sheath.
Heart valve replacement is necessary where the native heart valve is damaged, mal- or nonfunctioning. In the heart, cardiac—or “aortic”—valves maintain the unidirectional flow of blood by opening and closing depending on the difference in pressure on each side.
The aortic valve can be affected by a range of diseases and can, therefore, require cardiac valve replacement, which means that a patient's aortic valve is replaced by a different valve. The valve can either become leaky, i.e. regurgitant or insufficient, in which case the aortic valve is incompetent and blood flows passively back to the heart in the wrong direction. Further, the valve can become partially shut, i.e. stenotic, in which case the valve fails to open fully, thereby obstructing blood flow out from the heart. The two conditions frequently co-exist.
There are two basic types of artificial heart valve, mechanical valves and tissue valves. Tissue heart valves are usually made from animal tissues, either animal heart valve tissue or animal pericardial tissue, which are treated to prevent rejection and to prevent calcification. Whereas mechanical valves generally are designed to outlast the patient, they have the drawback that due to their material there is an increased risk of blood clots forming, which may only be prevented by a constant anti-coagulant therapy, which makes the patient more prone to bleeding. Mechanical heart valves are generally composed entirely of synthetic or nonbiological materials, whereas tissue (or bioprosthetic) heart valves are composed of synthetic and biological materials. Bioprosthetic cardiac valves can either represent xenografts, which are taken from different species than the recipient, or homografts, which are donor valves taken from the same species as the recipient. Generally, the artificial valves comprise expandable stent systems which are introduced into the vessel in a compressed state and which are allowed to expand by removal of compressive structures.
Aortic valve replacement traditionally requires median sternotomy and thus open heart surgery, which is a major impact on the patient to be treated: The chestbone is sawed in half and after opening of the percardium, the patient is placed on a cardiopulmonary bypass machine. Once the patient is on bypass, the patient's diseased aortic valve is removed and a mechanical or tissue valve is put in its place. Besides the physical stress associated with this operation, there is a risk of death or serious complications from open heart surgery, in particular depending on the health and age of the patient.
However, recently, valves are developed that can be implanted using a catheter or deployment systems without open heart surgery, and the deployment of the prosthesis can either be achieved retrograde, i.e. against normal blood flow, or antegrade, with blood flow.
International patent application WO 2008/070797 discloses a system and a method for transapical delivery of an annulus anchored self-expanding valve. The system disclosed therein comprises a catheter assembly having an outer sheath, an elongate pusher tube and a central tube. At the distal end of the central tube an atraumatic tip is provided; in the loaded state, the prosthesis is carried adjacent to the tip on the central tube and compressed by the sheath. Upon retraction of the sheath, the distal end of the prosthesis, i.e. the one that is located nearest to the tip is released and the prosthesis is allowed to expand. Subsequently, the sheath gets completely pulled back to fully release the prosthesis, which subsequently, in case of as self-expanding prosthesis, can fully expand, or which can be expanded by using a balloon.
Similarly, WO 2007/098232 discloses a deployment device for self-expanding prostheses, wherein the device comprises a split sheath by means of which the prosthesis can be deployed in several steps.
Despite the many different deployment systems and techniques known in the art, the precise deployment with the possibility to move the prosthesis once partially deployed still remains a crucial step and is difficult to achieve with the systems, devices and methods presently available. In addition, a major disadvantage of the presently used systems for deploying self-expandable valves is, that upon deployment the proximal end of the prosthesis, which has to be deployed first, flares and, thus, forms a “parachute” thus obstructing the blood flow. Due to this fact, the operator, e.g. a surgeon, is necessitated to work and deploy the prosthesis under time pressure and fast to avoid disruption of normal blood flow.